The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Continuous media recording systems write data to a disk in a continuous pattern. Prior to a write operation, servo sector information (e.g., preamble data, synchronization marks, and positioning information) is read from a disk. The servo sector information is used to position a read/write head and to correct bit positioning error. Bit positioning error refers to a difference between (i) the true bit position on a disk that data is stored (or is to be stored) and (ii) the read/write head position. Subsequent to correcting bit positioning error, data is written to sectors of the disk at a desired position. Since data is written to the disk in a continuous pattern, the data may be written generally at any point within a sector of the disk.
Bit-patterned media (BPM) recording systems provide increased storage capacity over continuous media recording systems. BPM recording systems may store as much as ten times more information on a magnetic storage device (e.g. a magnetic disk or hard disk) than continuous media recording systems. As an example, a BPM recording system may store 1 or more terabits (Tbit) of data in one square inch (in2) of a magnetic storage device.
BPM recording systems write data to a disk in discontinuous island-based patterns. Bits of data are stored at specific points or discrete bit islands on the disk. For example, each bit island may store 1 bit of data. Bit positioning accuracy requirements of bit-patterned media recording systems are more stringent than that of continuous media recording systems. This assures that data is written over bit island areas of the disk while minimizing and/or avoiding attempts to write data over areas between bit islands.
A BPM recording system may include a servo clock and a write clock. The servo clock may be used for timing read events of servo sector information from the disk. The write clock may be used for timing write events including positioning and access timing of a write head. Synchronization of the write clock with the patterned media is needed in a BPM recording system due to the discontinuous format of BPM. A write clock signal is synchronized when rising and/or falling edges of the write clock signal are aligned with start and end positions of the bit islands, such that writing occurs over the bit islands and not over areas between bit islands.